With reference to FIG. 1, scaffolds of steel usually comprise two frames 1 and 1a formed with vertical poles 11 and horizontal rods 12, and connecting members 13 arranged crosswise between the frames 1 and 1a and detachably held thereto. The vertical poles 11 are provided with retaining devices 2 for retaining the ends of the connecting members 13 thereon.
The retaining device 2 must be so adapted that the connecting member 13, once mounted thereon, can be held in place during usual use but is still easily detachable therefrom when disassembling the scaffold. FIG. 11 shows conventional retaining device which fulfil the above requirement.
The retaining device 2a shown in FIG. 11 comprises a hollow rod portion 41 to be secured to the frame 1 and formed with an axial slit 33. A pawl plate 34 fitted in the slit 33 is projectable from and retractable into the rod portion. On one side of the rod portion opposite to the slit 33, the rod portion is indented from outside to provide a stopper 35 for the pawl plate 34 for preventing the plate from slipping off. A leaf spring 5 housed in the rod portion 41 biases the pawl plate 34 outward. The rod portion 41 is welded at its base end to the frame 1.
To mount the connecting member 13 on the device 2a, the member 13 is passed over the forward end of the rod portion 41 through a hole 14 of the member 13 and forced toward the base end of the rod portion 41. The pawl plate 34 therefore retracts into the portion 41 against the spring 5 and thereafter returns upon the member 13 passing over the pawl plate 34, preventing the connecting member 13 from slipping off.
Although the retaining device 2a has the advantage that the connecting member 13 is easily mountable on and detachable from the rod portion, they are difficult and expensive to make since the slit 33 must be formed by machining as by milling.
With the device, the rod portion having the pawl plate 34 fitted in the slit 33 must be indented from outside with a chisel to form the stopper 35 on one side thereof opposed to the slit 33. This procedure is difficult to follow.
Further when the frame 1 provided with retaining devices 2a is subjected to hot dipping or coating operation for the inhibition of corrosion, the operation entails the problem that the molten metal or coating composition ingressing into a clearance between the plate 34 and the cutout portion 33 solidifies, restraining the plate 34 against pivotal movement.